The present invention relates to a device for an extensible fin blade on a unit in the form of a shell, projectile, missile etc.
The invention is intended, inter alia, for use on fin-stabilized shells which are provided with a number of main fins, which are arranged with full-calibre dimensions so that they will be guided in the bore of the barrel when the shell is fired. In certain connections, for instance in the case of supersonic shells, for stabilization reasons and weight-reduction reasons, there is a desire to have the centre of pressure in the shell located as far to the rear in the shell as possible, without the length of the shell being increased substantially. A possibility of complying with this requirement is to make the fin arrangement extensible, so that parts of the fins exceed the full calibre after the shell has been fired from the barrel in question.
The present invention is directed towards this fact, which is known in itself, and proposes a specific arrangement of fins in which the respective main fin should be made with a recess in which the fin blade in question is supported so that it is movable from a retracted first position to an extended second position. In further developments of the concept of the invention it is also proposed how the extension function should be achieved and the second position be made distinct.